This application claims the priority benefit of Taiwan application serial no. 90109097, filed Apr. 17, 2001.
1. Field of the Invention
The invention relates in general to a method of optimal power calibration. More particularly, the invention relates to a method of optimal power calibration that can derive required optimal recording power for any recording position of an optical storage disk such as a rewritable disk.
2. Description of the Related Art
Rewritable disks (CD-RW) and the recordable disks (CD-R) are currently popular optical storage media for data storage that a rewritable disk can vary or rewrite data stored inside, while the recordable disk can be used to record data only once. Both the rewritable and recordable disks have to undergo an optimal power calibration (OPC) process to obtain required optimal recording powers before being used. FIG. 1 illustrates the operating flow of the conventional OPC process, which is basically performed on a power calibration area (PCA) allocated on an inner track of the disk. In step 100, the recording head jumps to the count area of the power calibration area, while the number of recorded blocks (indicating the number of times that the OPC process has been performed) is read for obtaining the address of the empty power calibration area on the disk in step 110. In step 120, the recording head jumps to the empty power calibration area and then starts to perform an OPC process in step 130. Under this OPC process, the recording head uses 15 (fifteen) different powers to write 15 frames of calibration data (or, OPC pattern, e.g., ATIP (Absolute Time In Pre-groove) information) into the empty power calibration area. The recording head jumps to positions where the written operations have just performed so that the calibration data can be read out for determining the optimal recording power in the following steps 140, 150 and 160. The recording head then moves to the count area of the last empty PCA in step 170 and registers that one more OPC process is performed in step 180. Finally, the measured optimal recording power is used to record user""s data onto the disk in step 190. All steps shown in FIG. 1 follow the specifications defined in the Orange Book for CD-RW disks. Obviously, the number of times stored in the count area should be increased in step 180 after an OPC process is performed, however, a rewritable disk may be re-burned for recording data about 100 times, typically.
Conventional approach for measuring required optimal recording power is only adapted to a constant linear velocity (CLV) mode rather than to a constant angular velocity (CAV) mode because the recording head follows different linear velocities on the inner and outer tracks under recording in CAV mode. The linear velocities under CAV mode are proportional to the distances between the recording positions (or, data blocks) to the center of the optical storage disk, while the velocities for recording the outer tracks can be as high as 2.5 times than that for recording the inner tracks. Such a difference may cause failures while recording the outer tracks by directly referring the optimal recording power derived from the power calibration area of the inner track. Although CLV mode is now the broadly used approach, however, it significantly consumes more recording time than that of the CAV mode. Additionally, even CLV mode is adopted everywhere of a disk, different materials coated on the inner and outer tracks of the disk should raise different requirements for recording. There is no solution now that overcomes data recording failures arisen from different material coated as aforementioned because the conventional OPC process can only find out the optimal power suitable for the inner tracks rather than the entire optical storage disk.
The principal object of the invention is to provide a method that takes the advantage of the rewritable characteristic to measure required optimal recording power for the entire rewritable disk. Any recording position on the rewritable disk may derive an optimal recording power suitable for itself when associated data recording operation is performed whether CLV or CAV mode is used. Additionally, those optical storage disks having different materials coated on the inner and outer tracks may easily employs the disclosed method for recording data stored thereon without causing unexpected failures.
The disclosed method can be applied to an optical storage medium such as a rewritable disk having a power calibration area in its inner track as a typical recordable disk does. In one embodiment, an originally optimal power calibration process is performed on the power calibration area allocated in the inner track by writing a plurality of calibration data (or, OPC pattern) burned therein. Thereafter, these written calibration data are read out for determining an originally optimal recording power suitable for the inner track. Several assisted optimal recording powers are successively derived from data blocks selected by following a predetermined rule under a plurality of assisted OPC processes. A relation curve can be built up by using these derived optimal recording powers to indicate the relationships between an optimal recording power of a recording position and a distance from the center of the optical storage disk to the recording position. Finally, a recording operation can be performed to the optical storage medium by mapping out required optimal recording powers from the relation curve. The disclosed method may efficiently upgrade data recording performance whether CAV or CLV mode is employed.
In one embodiment, a xe2x80x9cSub Q code mode 0xe2x80x9d pattern defined in the Orange Book is adopted as the OPC pattern for written into the rewritable disk under the assisted OPC processes. This xe2x80x9cSub Q code mode 0xe2x80x9d pattern indicates an xe2x80x9cerasable statexe2x80x9d or xe2x80x9cerasable patternxe2x80x9d which may be overwritten by sequentially recording data, so that these OPC patterns recorded under assisted OPC processes will be erased instead of being incorrectly recognized as normal data in the future. The disclosed method takes the advantage of the rewritable characteristics defined in the Orange Book to measure the optimal recording power for any recording position of the rewritable disk. Consequently, all data recording operations can be performed on all recording positions (or, data blocks) of the rewritable disk by mapping out required optimal recording powers from the established relation curve whatever CLV or CAV mode is used.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.